BDNF and glaucoma: In a targeted approach, the levels of the brain-derived neurotrophic factor (BDNF)—a vital component for the survival and differentiation of neurons—were determined by ELISA in the tears of NTG patients (n = 20) and control subjects (n = 20), observing a significant upregulation in glaucomas (3.2-fold), with potential use as a biochemical marker for early detection of NTG, in combination with other markers [139].